Exchange 2010 SP3 Upgrade

DiscoverySearchMailbox is causing the issue.
Simply remove the account and re-create it.

•Reboot the server before you start to clear any pending reboots
•Right click to Discovery Search Mailbox and remove, object is going to be under Disconnected Mailboxes
•Confirm AD object is also deleted.
•Reboot (to make replication faster)
•Run SP3 setup
•Complete
•Now you need to re-create AD object first
•Run setup.com /preparead from the location where you have run sp3 upgrade
•Complete
•Confirm AD object has been created.
•Go to properties of new discoverysearchmailbox AD user and copy the ID. It looks like something like this DiscoverySearchMailbox {D919BA05-46A6-415f-80AD-7E09334BB852}
•Open Exchange Management Shell and type this line
•Enable-Mailbox –Discovery “DiscoverySearchMailbox {D919BA05-46A6-415f-80AD-7E09334BB852}”
•Confirm mailbox is created and you are all done.
•Now if you want you can cleanup the old discoverysearch from disconnected mailboxes by using command line.
•Remove-StoreMailbox -Database “mailbox database name where it was” -Identity “Discovery Search Mailbox”
•State: Disabled
•Confirm: YES
•Done.